Mannequin Henry Gaffney

The song was written by Henry Gaffney. 

Henry is an American  singer songwriter and composer. Initially he wrote and released his own music in the late 70s but then began writing for other people. Most notably he wrote for The Pointer Sister, The Four Tops, Roberta Flack and Glen Campbell. 

He wrote a number of songs for "Fame" including "There's A Train", "Manhattan" and "Come What May".